Flexible circuit structures, or “flexible circuits” for short, are used in a variety of applications, including, for example, automotive, portable computers, cameras, and military and avionics. Flexible circuits offer a compact footprint and reduced weight as compared to circuits built on rigid substrates. In applications in which a rigid planar structure would not physically fit in the desired space or in applications in which the circuit structure is repeatedly flexed during use, flexible circuits meet requirements that rigid structures cannot.
In applications involving repeated flexing of the flexible circuit, designers give particular attention to the durability of the structure of the flexible circuit. Through repeated flexing, a flexible circuit may fail, such as with broken conductors on the flexible substrate of the flexible circuit. In an effort to add durability, the conductors of the flexible substrate may be placed near the neutral axis of the flexible circuit, which may require additional dielectric layers over the conductors.